The present invention relates to apparatus and methods for filtering or removing matter from within a vascular system. More particularly, the present invention provides a low profile self-expanding vascular device useful for capturing emboli or foreign bodies generated during interventional procedures, and for thrombectomy and embolectomy.
Percutaneous interventional procedures to treat occlusive vascular disease, such as angioplasty, atherectomy and stenting, often dislodge material from the vessel walls. This dislodged material, known as emboli, enters the bloodstream, and may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. The resulting ischemia poses a serious threat to the health or life of a patient if the blockage occurs in critical tissue, such as the heart, lungs, or brain.
The deployment of stents and stent-grafts to treat vascular disease, such as aneurysms, also involves the introduction of foreign objects into the bloodstream, and also may result in the formation of clots or release of emboli. Such particulate matter, if released into the bloodstream, also may cause infarction or stroke.
Furthermore, interventional procedures may generate foreign bodies that are left within a patient""s bloodstream, thereby endangering the life of the patient. Foreign bodies may include, for example, a broken guide wire, pieces of a stent, or pieces of a catheter.
Numerous previously known methods and apparatus have been proposed to reduce complications associated with embolism, release of thrombus, or foreign body material generation. U.S. Pat. No. 5,833,644 to Zadno-Azizi et al., for example, describes the use of a balloon-tipped catheter to temporarily occlude flow through a vessel from which a stenosis is to be removed. Stenotic material removed during a treatment procedure is evacuated from the vessel before the flow of blood is restored. A drawback of such previously known systems, however, is that occlusion of antegrade flow through the vessel may result in damage to the tissue normally fed by the blocked vessel.
U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli filter system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and any interventional devices, such as angioplasty balloons or stent delivery systems, are advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter. Similar filter systems are described in U.S. Pat. No. 4,723,549 to Wholey et al. and U.S. Pat. No. 5,827,324 to Cassell et al.
One disadvantage of radially expandable filter systems such as described in the foregoing patents is the relative complexity of the devices, which typically comprise numerous parts. Connecting more than a minimal number of such parts to a guide wire generally increases delivery complications. The ability of the guide wire to negotiate tortuous anatomy is reduced, and the profile of the device in its delivery configuration increases. Consequently, it may be difficult or impossible to use such devices in small diameter vessels, such as are commonly found in the carotid artery and cerebral vasculature. Moreover, such filter devices are generally incapable of preventing material from escaping from the filter during the process of collapsing the filter for removal.
International Publication No. WO 98/39053 describes a filter system comprising an elongated member, a radially expandable hoop and a cone-shaped basket. The hoop is affixed to the elongated member, and the cone-shaped basket is attached to the hoop and the elongated member, so that the hoop forms the mouth of the basket. The filter system includes a specially configured delivery catheter that retains the mouth of the basket in a radially retracted position during delivery.
While the filter system described in the foregoing International Publication reduces the number of components used to deploy the cone-shaped basket, as compared to the radial strut-type filter elements described hereinabove, it too has drawbacks. Chief among these, it is expected that it will be difficult to reduce the diameter of the radially expandable hoop to its retracted position. In particular, as the hoop is contracted through smaller radii of curvature, the stiffness of the hoop is expected to increase dramatically. This increased stiffness prevents the hoop from being contracted more tightly, and is expected to result in a delivery profile too large to permit use of the device in critical regions of the body, such as the smaller coronary arteries, carotid arteries, and cerebral vasculature.
In view of the foregoing disadvantages of previously known apparatus and methods, it would be desirable to provide a vascular device, e.g., for use as a vascular filter, that overcomes such disadvantages and employs few components.
It would be desirable to provide a reliable and multi-functional delivery system for use with the vascular device.
It would be desirable to provide an integrated vascular device with a thrombectomy element and a vascular filter.
It also would be desirable to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels.
It further would be desirable to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters.
It still further would be desirable to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
It also would be desirable to provide a vascular device that permits a rapid exchange deployment modality.
In view of the foregoing, it is an object of the present invention to provide a vascular device that overcomes disadvantages of previously known vascular filters, thrombectomy/embolectomy and foreign body removal devices, and employs few components.
It is an object of the present invention to provide a reliable and multi-functional delivery system for use with the vascular device.
It is an object to provide an integrated vascular device with a thrombectomy element and a vascular filter.
It also is an object of this invention to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels.
It is a further object to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters.
It is another object to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
It also is an object to provide a vascular device that permits a rapid exchange deployment modality.
These and other objects of the present invention are accomplished by providing a vascular device, suitable for use as a vascular filter or thrombectomy/embolectomy device that comprises a blood permeable sac affixed at its perimeter to a support hoop having an articulation region. The support hoop is attached to a distal region of an elongated member, such as a guide wire, and supports a proximally-oriented mouth of the sac when the device is deployed in a vessel. The device may also comprise a nose cone to facilitate percutaneous introduction, and a delivery sheath having one or more lumens. The lumens may further be configured for a rapid exchange mode of introduction along the guide wire.
In a first embodiment, the support hoop includes one or more reduced-thickness articulation regions that enable the support hoop to be contracted to very small radii of curvature without the problems of increased stiffness and kinking of previously known devices. In an alternative embodiment, the articulation region may comprise a gap in the support hoop bridged by the perimeter of the blood permeable sac.
The support hoop preferably also has a curved profile that prevents the articulation region, when folded, from damaging the wall of the vessel. The curved profile permits the device to effectively contact the walls of the vessel and reduce emboli or thrombus removed from the vessel wall from bypassing the sac. Moreover, the articulation region, when combined with a support hoop having a curved profile, causes the sides of the support hoop to fold inwards towards one-another when the vascular device is collapsed into a sheath for removal. This, in turn, closes the mouth of the sac and reduces the potential for emboli or thrombus to be released from the vascular device during removal.
Advantageously, use of an articulation region permits vascular devices of the present invention to be contracted to very small diameters, thereby enabling the use of delivery catheters having diameters as small as 3 Fr. Moreover, the vascular devices may be retracted within the guide wire lumens of conventional treatment devices, such as angioplasty catheters and stent delivery systems, thereby obviating the need to re-insert a specialized delivery catheter to remove the vascular device. However, a retrieval sheath having a distal region that flares or expands outwardly to receive the emboli-filled sac upon completion of an interventional procedure, and which reduces risk of rupture to the sac, optionally may be provided in accordance with the present invention.
In embodiments suitable for use as embolic filters, the vascular device may include a separate guide wire for introducing treatment devices proximal of the deployed vascular device. Additionally, the vascular device may have a second support hoop attached to the distal end of the sac. During retrieval, multiple hoops ensure that emboli are retained within the sac and prevent the sac from bunching. Where multiple hoops are rotated, they may be arranged such that they rotate independently of the guide wire, thereby reducing risk that the sac wall will become twisted during advancement.
In alternative embodiments, sac bunching is mitigated by tapering the sac and attaching it to one or more support hoops, or to the guide wire. Sac porosity may also be specified to ensure passage of blood cells and capture of emboli, as well as to control a pressure drop across the vascular device. In other embodiments, a delivery sheath is provided that permits a lesion to first be crossed with an unencumbered guide wire prior to passing the vascular device across the lesion. In still further embodiments, several support hoops may be provided at the mouth of a single sac to facilitate opening and closing of the sac.
In thrombectomy applications, a separate thrombectomy element may be provided in addition to the vascular filter. The thrombectomy element may be attached to the elongated member proximal of the vascular filter or may comprise a separate catheter. In a preferred embodiment, the thrombectomy element is similar in construction to the vascular filter and may be retracted independently. Alternatively, the thrombectomy element may be any conventional atherectomy device used in conjunction with the vascular filter and may be advanced and retracted either in conjunction or independently of the vascular filter.
A delivery system in accordance with the present invention, configured for use with the vascular devices described herein, is also provided. The delivery system integrates the functions of a Touhy Borst, a torquer, and a pusher into a single device, thereby facilitating introduction and retrieval of embodiments of the present invention. The torqueing function allows a vascular device to navigate tortuous anatomy. For example, the distal end of a guide wire may be rotated to selectively orient the vascular device in a selected branch of a bifurcated vessel.
The Touhy-Borst adapter permits liquid to be introduced or withdrawn through the lumen of the vascular device delivery catheter. The pusher feature of the delivery system allows deployment and retraction of the vascular device from within the delivery catheter.
Methods of using embodiments of the present invention are also provided, including use of novel radiopaque features, and use of a previously known balloon catheter to arrest antegrade flow through a vessel until the vascular device of the present invention is deployed.